Polishing pad and method of producing the same

ABSTRACT

The present invention mainly relates to a polishing pad and method of producing the same. The polishing pad comprises a base material having a surface for polishing a substrate, wherein the surface comprises a non-woven fabric and an elastomer. The non-woven fabric is made of a long fiber and the elastomer is embedded into the fabric.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing pad for use in a chemical mechanical polishing, and a method of producing the polishing pad.

2. Description of the Related Art

Chemical mechanical polishing (CMP) is a procedure for planarizing the surface of a substrate with a polishing pad. CMP is generally applied to polishing lens, mirrors, substrates of liquid crystal displays, silicon wafers, and oxidation and/or metal layers on silicon wafers.

Taking silicon wafers as an example, ingots of monocrystalline silicon are sliced first. The wafers are usually lapped to make them flat for subsequently chemical etching. A polishing process is required after the etching process. During the polishing process, a polishing pad together with slurry reacts chemically with the silicon atoms on the surface of the wafer to make the reacted surface softer than the underlying silicon. Furthermore, the reacted surface is continually wiped away causing fresh silicon to be exposed to the slurry and the polishing pad.

A conventional polishing pad comprises a base material having a surface for polishing a substrate. The surface comprises fabric and an elastomer embedded into the fabric. Fibers of the fabric along with the elastomer have the functions of carrying the slurry and removing the reacted surface from the wafer in the polishing process. The nonwoven fabric is commonly used in the base material. A conventional nonwoven fabric uses directional or non-directional short fibers (usually having a length of less than 10 cm) for forming fabric without weaving. According to the manner of forming the fabric, the nonwoven fabric usually comprises composite nonwoven fabric, needle-punched nonwoven fabric, melt-blown nonwoven fabric, spunbonded nonwoven fabric, dry-laid nonwoven fabric, wet-laid nonwoven fabric, stitch bonded nonwoven fabric, and spunlace nonwoven fabric. However, the short fibers should be made through a cording process, and a needle-punching process is also needed when manufacturing needle-punched nonwoven fabric. Such processes result in an uneven distribution of the fibers, and aggregations of fibers are easily observed in a nonwoven fabric. In addition, a breakage of the fibers also occurs due to these processes. Furthermore, after embedding the elastomer into the fabric, the uneven distribution of the elastomer due to the uneven distribution of the fibers affects the cell size made of the fibers and the elastomer, hardness, uniformity, density of the elastomer, and thickness, and the slurry cannot flow smoothly and polishing particles in the slurry cannot diffuse evenly. Balling is commonly observed when polishing. Besides, the residues formed during polishing tend to stay on the surface of the polishing pad and their removal is difficult; as a result, the residues scrape and damage the substrate to be polished.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a polishing pad comprising a base material having a surface for polishing a substrate, wherein the surface comprises non-woven fabric and an elastomer. The non-woven fabric is made of a long fiber, and the elastomer is embedded into the fabric.

Another object of the present invention is to provide a method of polishing a substrate. The method comprises a step of using the polishing pad mentioned above to polish a surface of the substrate.

Still another object of the present invention is to provide a method of producing the polishing pad described above. The method comprises steps of: (a) providing the base material comprising the non-woven fabric made of the long fiber; (b) impregnating the surface of the base material with an elastomer solution; and (c) curing the elastomer impregnated in the surface of the base material.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a polishing pad comprising a base material having a surface for polishing a substrate, wherein the surface comprises non-woven fabric and an elastomer. The non-woven fabric is made of a long fiber, and the elastomer embedded into the fabric.

As used herein, “non-woven fabric” refers to a manufactured sheet, web or mat of directionally or randomly orientated fibers, bonded by friction, and/or cohesion and/or adhesion, excluding paper and products which are woven, knitted, tufted, stitch-bonded incorporating binding yarns or filaments, or felted by wet-milling, whether or not additionally needled. The fibers may be of natural or man-made origin. They may be staple or continuous filaments or be formed in situ. According to the method of forming the web, the non-woven fabric usually comprises composite nonwoven fabric, needle-punched nonwoven fabric, melt-blown nonwoven fabric, spunbonded nonwoven fabric, dry-laid nonwoven fabric, wet-laid nonwoven fabric, stitch bonded nonwoven fabric, and spunlace nonwoven fabric. Compared with woven fabric, the non-woven fabric has a better material property.

In one preferred embodiment of the invention, the non-woven fabric is used in a roll-to-roll manner that improves batch uniformity.

As used herein, the term “fiber” refers to a single fiber or composite fibers, preferably composite fibers. The fiber is selected in accordance with the substrate to be polished. The fibers of the surface of the base material provide protrusions for polishing and also provide a scaffold allowing the elastomers deposed in the space defined by the scaffold. Artisans skilled in this field can choose suitable kinds of fibers and coordinate the elastomer polymer with the fibers according to the disclosure of the specification. Preferably, the long fiber is made of at least one material selected from the group consisting of polyamide, terephthalamide, polyester, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, and mixtures thereof.

As defined in this field, the term “long fiber” refers to a fiber having a length more than 10 cm. The shape of the long fiber is continuous and the length is unlimited in theory. The long fiber is easily twisted for improving the strength and stress.

In one preferred embodiment of the invention, the fiber is a sea-island fiber. As used herein, the term “sea-island fiber,” also known as “sea-island type composite fiber,” refers to a fiber comprising a sea component and an island component. For example, the sea-island fiber is produced by conjugate-spinning or blend-spinning two polymers in a sea-island manner. In one preferred embodiment of the invention, the sea-island fiber is treated by weight reducing to reduce the proportion of the sea component. The methods of weight reducing the sea component are well known to artisans skilled in this field, such as those methods using sodium hydroxide or toluene. Preferably, the long fiber after reducing the sea component is divided into 0.05 to 0.0001 Deniers.

In one preferred embodiment of the invention, the non-woven fabric comprises a net frame. As used herein, the term “net frame” refers to a thin and strengthened material designed for improving the strength of the non-woven fabric according to the invention. The material of the net frame is preferably polyamide, polyester, or polyolefin. The net frame is preferably made of the long fiber. Fibers can be woven or non-woven to form the net frame. In order to allow the long fibers to form the non-woven fabric according to the invention, the net frame comprises meshes, and the fibers of the net frame and the long fibers of the non-woven fabric are intertwined with each other. Preferably, the net frame has a thickness of 0.01 to 1.0 mm. The net frame has a weight per area unit of 10 to 200 g/m². In addition, the net frame has a mesh of 10 to 150.

As used herein, the term “elastomer,” also known as “elastic polymer,” refers to a type of polymer that exhibits rubber-like qualities. 5 When polishing, the elastomer serves as a good buffer to avoid scraping the surface of the substrate to be polished. In one preferred embodiment of the invention, the elastomers are foam resins. As used herein, the term “foam resin” refers to a material containing a thermoplastic resin and a thermodecomposing foaming agent. Preferably, the elastomers are at least lo one selected from the group consisting of polyurethane, polyamide, polycarbonate, polyaminonitrile, polymethacrylate, epoxyl resin, phenolic resins, polymethyl methacrylate, polyaminoester, vinylbenzene polymer, acrylic resin, and polyurethane.

The polishing pad according to the invention can avoid the defects of the conventional polishing pad made of short fibers. Because the long fibers are able to form non-woven fabric without a cording process or a needle-punching process, the uneven distribution of the fibers, aggregations of fibers and a breakage of the fibers due to the processes are then avoided. As a result, the elastomer according to the invention is evenly embedded into the non-woven fabric. Furthermore, the cell size made of the fibers and the elastomer, hardness, uniformity, density of the elastomer, thickness, compression ratio, and recover rate after compression are all improved. The slurry can flow smoothly and polishing particles can diffuse evenly as well. The polishing pad according to the invention does not damage the surface of the substrate to be polished and balling is diminished dramatically. Furthermore, the polishing efficiency is satisfied when the polishing pad according to the invention is applied.

The present invention also provides a method of polishing a substrate. The method comprises a step of using the polishing pad as mentioned above to polish a surface of the substrate.

The present invention further provides a method of producing the polishing pad as mentioned above. The method comprises steps of: (a) providing the base material comprising the non-woven fabric made of the long fiber; (b) impregnating the surface of the base material with an elastomer solution; and (c) curing the elastomer impregnated in the surface of the base material.

In step (b) of the method, the manner of impregnating the base material with an elastomer solution is the method of dipping the non-woven fabric with the elastomer solution. The conditions for impregnation are well known to artisans skilled in this field. Suitable solvents used in the elastomer solution include dimethylformamide (DMF). The elastomer solution optionally comprises additives such as a detergent. Preferably, the elastomer has a concentration ranging from 2 wt % to 60 wt % in the elastomer solution.

Preferably, step (b) further comprises impregnating the entire base material with the elastomer solution.

In step (c) of the method, the manner of curing the elastomer impregnated in the base material is to cure the elastomer in the non-woven fabric. In one embodiment of the invention, the base material is put into a curing solution for curing. Preferably, the curing solution comprises 0 to 40 wt % dimethylformamide in water. The conditions for curing are well known to artisans skilled in this field. Preferably, the curing is carried out at room temperature and pressure.

In one preferred embodiment of the invention, the method of producing a polishing pad further comprises a step (c1) of washing the base material after step (c). The purpose of washing is to remove residues from the polishing pad. In one embodiment of the invention, water is used in washing and extrusion wheels are optionally used. The conditions for washing are well known to artisans skilled in this field. Preferably, the base material is washed in water at 50 to 90° C. and then subjected to the extrusion wheels several times.

In one more preferred embodiment of the invention, the method of producing a polishing pad further comprises a step (c2) of drying the base material after step (c1). The purpose of drying is to remove the excess solvent from step (c1). The conditions for drying are well known to artisans skilled in this field. In one embodiment of the invention, the drying is air-drying, and the drying temperature is in the range of 100° C. to 160° C.

Preferably, the method of producing a polishing pad further comprises a step (c3) of mechanically polishing the surface of the base material and the elastomer. For example, the mechanical polishing can be accomplished using a sand blast. The conditions for mechanical polishing are well known to artisans skilled in this field. More preferably, the fibers are exposed to the surface of the base material after mechanical polishing.

In one preferred embodiment of the invention, steps (b) and (c) are repeated several times. The kind of the elastomer used in each time can be different or the same.

The following Examples are given for the purpose of illustration only and are not intended to limit the scope of the present invention.

EXAMPLE

Base Material. A polyethylene terephthalate chip was melt spun at 260° C. to 300° C. and quenched at room temperature. The chip was then subjected to a calender machine to obtain a base material with 10 to 150 meshes and having a thickness of 0.7 mm and a weight of 150 g/m².

Net Frame. A fabric was slivered for to obtain a net. Several sheets of the net were laid up and then woven with 70 Deniers of Nylon 6 yarn to obtain a 30-mesh sheet having a thickness of 0.15 mm and a weight of 35 g/m². The sheet was then needle punched (700 times/m²) to obtain a net frame with a weight of 475 g/m².

Impregnating. The base material was impregnated in an elastomer solution with a viscosity of 700 to 850 Cps. The elastomer solution comprises 50 wt % of polyurethane, 49 wt % of dimethylfolmamide and 1 wt % of detergent.

Curing. The base material, after impregnating, was put into a curing solution comprising 25 wt % dimethylformamide in water to mold the elastomer impregnated in the fibers.

Washing. The residues and the excess curing solution were removed by extrusion wheels. The base material was then washed in water at 80° C. and then subjected to the extrusion wheels several times.

Drying: The base material, after washing, was then dried at 140° C.

Publishing. After drying, the base material was subjected to mechanical polishing with #150 and #400 sand paper at 1200 and 1300 rpm, and a 1.28 mm product with a flat surface was obtained.

Assay: The polishing pad with a long fiber according to the invention (long fiber) and a conventional polishing pad with a short fiber (short fiber) was assayed and the results are shown in Table 1. The compression ratio and recover rate after compression of the polishing pad according to the invention are both improved compared with the conventional polishing pad.

TABLE 1 Thickness Compression Recover rate after (mm) ratio (%) compression (%) Long fiber 1.40 19.63 92.34 Short fiber 1.35 15.99 89.67

While embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by persons skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention is not limited to the particular forms as illustrated, and that all the modifications not departing from the spirit and scope of the present invention are within the scope as defined in the appended claims. 

1. A polishing pad comprising a base material having a surface for polishing a substrate, wherein the surface comprises non-woven fabric and an elastomer, the non-woven fabric is made of a long fiber and the elastomer is embedded into the fabric.
 2. The polishing pad according to claim 1, wherein the long fiber is selected from the group consisting of a single fiber and composite fibers.
 3. The polishing pad according to claim 1, wherein the long fiber is made of at least one material selected from the group consisting of polyamide, terephthalamide, polyester, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, and mixtures thereof.
 4. The polishing pad according to claim 1, wherein the length of the long fiber is more than 10 cm.
 5. The polishing pad according to claim 1, wherein the long fiber is a sea-island fiber.
 6. The polishing pad according to claim 1, wherein the non-woven fabric comprises a net frame.
 7. The polishing pad according to claim 6, wherein the net frame is made of the long fiber.
 8. The polishing pad according to claim 1, wherein the elastomer is a foam resin.
 9. A method of polishing a substrate, the method comprising a step of using the polishing pad according to claim 1 to polish a surface of the substrate.
 10. A method of producing the polishing pad according to claim 1, comprising steps of: (a) providing the base material comprising the non-woven fabric made of the long fiber; (b) impregnating the surface of the base material with an elastomer solution; and (c) curing the elastomer impregnated in the surface of the base material.
 11. The method according to claim 10, wherein the long fiber is selected from the group consisting of a single fiber and composite fibers.
 12. The method according to claim 10, wherein the long fiber is made of at least one material selected from the group consisting of polyamide, terephthalamide, polyester, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, and mixtures thereof.
 13. The method according to claim 10, wherein a length of the long fiber is more than 10 cm.
 14. The method according to claim 10, wherein the long fiber is a sea-island fiber.
 15. The method according to claim 10, wherein the non-woven fabric comprises a net frame.
 16. The method according to claim 15, wherein the net frame is made of the long fiber.
 17. The method according to claim 10, wherein the elastomer is a foam resin.
 18. The method according to claim 10, further comprising a step (cl) of washing the surface of the base material after the step (c).
 19. The method according to claim 18, further comprising a step (c2) of drying the surface of the base material after the step (c1).
 20. The method according to claim 10, further comprising a step (c3) of mechanically polishing the surface of the base material and the elastomer after the step (c). 